Genetic Variation & Allelic Frequency in Bunnies Lab
Introduction:
In this activity, you will examine natural selection in a
small population of wild rabbits. Evolution, on a genetic
level, is a change in the frequency of alleles in a population
over a period of time. Breeders of rabbits have long been
familiar with a variety of genetic traits that affect the
survivability of rabbits in the wild, as well as in breeding
populations. One such trait is the trait for furless rabbits
(naked bunnies). This trait was first discovered in England
by W.E. Castle in 1933. The furless rabbit is rarely found in
the wild because the cold English winters are a definite
selective force against it.
In this activity, the dominant allele for normal fur is represented by F and the
recessive allele for no fur is represented by f. Organisms have two alleles for every trait
inherited. Bunnies that inherit two F alleles or one F allele and one f allele have fur,
while bunnies that inherit two f alleles have no fur.
Problem: How does natural selection affect allelic frequency over several generations?
Procedure:
1. Based on the information in the introduction, write a hypothesis in the form of an
If…then….because statement predicting which allele F or f will be more frequent in the
population over ten generations.
2. The kidney (red) beans represent the allele for fur (F), and the lima (off white) beans
represent the allele for no fur (f). The container represents the English countryside,
where the rabbits randomly mate.
3. There are three cups labeled. One cup is labeled FF for the homozygous dominant
genotype. The second cup is labeled Ff for the heterozygous genotype. The third cup is
labeled ff for those rabbits with the homozygous recessive genotype.
4. From the center bowl, count out 50 red beans and 50 off white beans.
5. Place the 50 red and 50 off white beans (alleles) in the brown paper bag and shake
up (mate) the rabbits.
6. Without looking at the beans, select two beans at a time. Record a tally on the
separate tally chart for generation 1. For instance, if you draw one red and one off
white bean, place a tally in the chart under "Number of Ff individuals." Place the beans
"rabbits" into the appropriate cup: FF, Ff, or ff.
7. Continue drawing pairs of beans and recording the tallies in the tally chart until all
beans have been selected and sorted.
8. Add up your tallies for each individual (FF, Ff, and ff) for generation 1. Record these
numbers in Data Table 1 on your answer sheet. (Please note that the total number of
individuals will be half the total number of beans because each rabbit requires two
alleles.)
9. The ff bunnies are born furless. The cold weather kills them before they reach
reproductive age, so they can't pass on their genes. Place the beans from the ff
container in the center bowl. You will NOT be counting these beans because they
represent bunnies that died.
10. Count the number of F alleles (beans) that were placed in both the FF cup and Ff cup
in the first round. Record the number of F alleles in Data Table 1 in the column labeled
“Number of F Alleles”. (this time, you are really counting each bean).
11. Count the number of f alleles that were placed in the Ff cup in the first round.
Record the number of f alleles in Data Table 1 in the column labeled “Number of f
Alleles”. (Don’t count the alleles of the ff bunnies because they are dead).
12. Total the number of F alleles and f alleles for the first generation and record this
number in the column labeled "Total Number of Alleles."
13. Place the alleles of the surviving rabbits (which have grown, survived and reached
reproductive age, FF and Ff) back into the brown paper bag and mate them again to get
the second generation.
14. Repeat steps six through fourteen for generations two through ten. Make sure
everyone in your group has a chance to either select the beans or record the results.
15. Determine the gene frequency. To find the gene frequency of F, divide the number
of F alleles by the total number of alleles, and to find the gene frequency of f, divide the
number of f alleles by the total number of alleles. Express results as a percentage.
Record the gene frequencies for F and f in Data Table 1 in the columns labeled "Gene
Frequency F" and "Gene Frequency f." The sum of the frequency of F and f should equal
one for each generation.
Gene Frequency F = total amount of F alleles
total amount of alleles (F + f for that generation)
Gene Frequency f = total amount of f alleles
total amount of alleles (F + f for that generation)
16. Graph your frequencies. Prepare a LINE graph with the horizontal axis as the
generation and the vertical axis as the gene frequency in %. Plot all frequencies on one
graph. Use two different colored lines for F and for f. Draw BEST FIT lines. Make a color
key and label your alleles. Be sure to title the graph and label the axes.
17. Complete the discussion questions.
Breeding Bunnies Data Collection & Analysis Worksheet
Hypothesis:
Data Table 1:
Generation
1
2
3
4
5
Number
of FF
individuals
Number of
Ff
individuals
Number of
ff
individuals
Number of
F Alleles
Number of
f Alleles
Total
Number of
Alleles
Gene
Frequency
of F
Gene
Frequency
of f
Name________________________________________Per._____________Date________
Analysis:
1. How does the number of alleles for the dominant characteristic compare with the number of
alleles for the recessive characteristic at the end of the lab?
2. What is happening to the frequency of the dominant allele during the lab? What is a
happening to the frequency of the recessive allele during the lab? Explain.
3. What does a change in allelic frequency indicate?
4. In a real rabbit habitat new rabbits often come into the habitat (immigrate), and others leave
the area (emigrate). How might emigration and immigration affect the gene frequency of F
and f in this population of rabbits?
5. How might you simulate the situation in question #4 if you were to repeat this activity?
6. How are the results of this simulation an example of natural selection? Give examples and
be specific.